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METALLURGY OF CAST IRON.
istry," published in Philadelphia in 1843, by Lee & Blanchard, says, page 385: " Iron expands in becoming solid, and therefore takes the impression of a mould with exactness.''
As the observation of this law was the basis upon which my experiments leading to the successful development of the contracting chill for cast iron car wheels was based, I am persuaded it will lead to many other practical results of great importance. This is my apology for trespassing upon your space and calling special attention to the matter.
The illustration seen in Fig. 73 is one the author dis-played in the A nierican Machinist, November i, 1894, to prove that the practice of casting bars between iron yokes, etc., prevented free action of the metal in expanding.
f A one-half-inch square test bar, twelve inches long, was used for an illustration. The author has tried by this device one-half-inch test bars without " gates," pouring them in "open sand" or without a cope, and cannot say he found much difference in their expansion. If any difference, the one with the gate showed the more. H is an iron block fitting tightly against the closed end of the flask. B is an iron block fitted loosely into a hole in the open end of the flask, as
FIG. 73-l at yz inch until 25 minutes 15 seconds after the mould was filled, when the galvanometer showed that contact with the gas carbon was broken and contraction had begun.